1. Field of the Invention
The present invention relates to a connecting structure of a crimp terminal and an electric wire.
2. Description of the Related Art
Reduction in the weight of a vehicle has a great influence on improvement of fuel consumption. Currently, reduction in carbon dioxide emission is required, and especially in an electric vehicle and a hybrid vehicle where the amount of wire harnesses used therein is larger than that in a gasoline-powered vehicle, it is preferable that an electric wire made of aluminum and an aluminum alloy of lightweight materials be used for a wire harness.
However, in an aluminum-made electric wire made of aluminum or an aluminum alloy being crimped and connected to a crimp terminal made of copper or a copper alloy, when water is in a part where the electric wire and the crimp terminal contact each other, this water serves as an electrolyte between dissimilar metals. In dissimilar metals such as a copper-made terminal and an aluminum-made conductor, when an electric circuit is formed through an electrolyte, corrosion of a metal having a baser potential (for example, the aluminum conductor) is accelerated due to difference in corrosion potential of the dissimilar metals. In other words, galvanic corrosion occurs.
A crimp terminal capable of preventing electric corrosion while ensuring conductivity even when an electric wire conductor crimped to the barrel pieces is made of a metal dissimilar to the barrel pieces has been disclosed (see Japanese Patent Application Laid-open No. 2012-69449, FIG. 7, paragraph 0113, for example).
A female crimp terminal (crimp terminal) 501 illustrated in FIG. 6 includes barrel pieces 507 making up a crimping portion 505 for enclosing and crimping the exposed part of an aluminum core 503, on both sides of the crimping portion 505 in the width direction. The barrel pieces 507 are made of a conductive metal that is dissimilar to the aluminum core 503, e.g., copper. A surrounding surface 509 of the crimping portion 505 includes an insulating coating portion 511 (or a water stop sheet, for example). The insulating coating portion 511 extends longer than the length of the exposed part of the aluminum core 503. A covered electric wire 513 is crimped by the barrel pieces 507 to the female crimp terminal 501 in such a manner that the crimping portion 505 integrally covers a range from a position ahead of the tip of the aluminum core 503 to the covered portion of the covered electric wire 513 on the tip end. In this manner, the aluminum core 503 and the crimping portion 505 are sealed by the insulating coating portion 511 or the water stop sheet that is a water-proofing material laid between the aluminum core 503 and the crimping portion 505, and is proofed against entrance of water, and therefore is protected against galvanic corrosion.
Given the female crimp terminal 501, a press with a swaging die is used to ensure electrical and mechanical performance achieved by the crimping the electric wire. With the female crimp terminal 501, when the aluminum core 503 is compressed with the swaging die, causing the aluminum core 503 to be crimped to and held by the crimping portion 505, the insulating coating portion 511 or the water stop sheet is also compressed. At this time, inside the crimp, the water stop sheet pushes a coating front end 515 (the cut surface of the coating of the stripped electric wire) in a direction extruding the coating out of the crimp. With the coating front end of the covered electric wire 513 pushed in a direction being extruded of the crimp, the crimping portion 505 can only be ensured of a smaller overlap width with respect to the crimped coating portion. Because the overlap width is reduced, the squeeze (the length in the extruded direction) of the water stop sheet positioned between the female crimp terminal 501 and the electric wire coating is also reduced. Furthermore, the overlap width required in ensuring sealing property may fall short, due to oscillations of the covered electric wire 513, or thermal expansion or contraction of the terminal/electric wire, for example.